Pneumatic compression device and methods for use in the medical field

ABSTRACT

A multi-faceted pneumatic medical device including a pump unit. together with housing therefor, that is adapted for cyclical compression of the human foot using an expandable fluid-tight bladder formed integral within a wrap that can be securely fastened onto the foot.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention The present invention relates generallyto a method and apparatus for cyclic compression of a body'sextremities, as well as a related system with a housing for containingand mounting the device on the foot board of a hospital bed.

[0002] 2. Related Art Medical devices that apply cyclic pressure to aperson's legs, arms. hands and/or feet are very old and well-known inthe art. Many have employed pulsating pads, pistons and plungers forimproving circulation. Others have used hydraulic and pneumatic bladdersfor similar purposes. The shapes, sizes, and composition of suchbladders, pads and the like are widely varied, depending largely ontheir particular application.

[0003] Man has known the fundamental principle of most cycliccompression devices for many years. They are merely a more recentembodiment of the old art of massage, which has probably been used tostimulate circulation for ages. Use of mechanical devices to effect themassaging action is obviously more recent, but has a clear history ofover a century.

[0004] Full understanding of the mechanism involved in this form ofimproving blood flow is more recent but has not fundamentally changedthe devices used to accomplish this result. Veins have long been knownto contain a series of one-way check valves along their length. Thus,when pressure is applied, compressing a vein, the fluid expelledtherefrom can only proceed in the direction of normal circulation. Whensuch compression is relaxed, the vein returns to its normal circularcross-section and the flow of blood into the vein is increased until itreaches its normal state of back pressure. Repeating this cycle in acyclic fashion thus increases blood flow in the normal direction ofcirculation.

[0005] Such compression/decompression cycles occur naturally in humansas part of the action of the muscles and flexure of the limbs. It hasbeen known for many decades that the foot includes a large venous plexus(or group of veins). It is also known that this venous plexus iscompressed during normal walking or running, thereby stimulatingcirculation. This efficient circulation aid is a marvelous design by ourCreator, as its effect is greatest when the leg muscles (the largestmuscles in the body) are in action and need the oxygen supplied byenhanced circulation.

[0006] For these and other reasons, the foot has long been known as aneffective site for applying cyclic pressure. For instance, many devicessuch as Massator's “PediPulsor” improve circulation by positioning apulsating, dome-shaped pad in the arch of the foot. Many others havetargeted the arch of the foot with flexible pneumatic chambers. Apartial sampling of such pneumatic devices that target the arch of thefoot are described in the masters thesis of James C. W. Parrott, B. Sc.,B. Sc. (Med.), M.D., entitled The Effect Of A Mechanical Venous Pump OnThe Circulation In The Feet In The Presenc Of Arterial Obstruction, anddated Oct. 1992 and found in the University of Manitoba library andincludes Japanese Utility Model No. 72-10392, U.S. Pat. No. 4,614,180 inthe name of Gardner and Fox, and U.S. Pat. No. 4,941,458 in the name ofTaheri.

[0007] Many others have long recognized that the foot contains veinsthat can be massaged or pumped to provide better circulation. Someexamples are: U.S. Pat. Nos. 3,824,992 and 3,901,221 to Nicholson, etal; Richard Dillon M.D. whose Journal of Vascular Diseases, Jan. 1986report on treatment of circulation-impaired patients states “compressionboot therapy enjoys a 173 year history;” and P Gaskell M.D. and J. C. W.Parrott M.D. whose Surgery, Gynecology and Obstetrics, Apr. 1978 report,which is a summary of Dr. Parrott's Master's Thesis, documented an earlydemonstration of the process of venous pumping with pulsed air bystating “We have found that the boot covering the foot alone is simpler,less cumbersome. and gives a greater reduction of venous pressure thaneither a large cuff which covers the whole calf or a boot which includesthe calf and the foot.”

[0008] Such devices and many other medical devices are typicallyauxiliary devices which may or may not be employed on each patient.Because of their auxiliary nature, it is beneficial for such devices tobe compact, portable and easily employed and stored adjacent a hospitalbed. Other devices have addressed such concerns with hooks that allowthe device to be hung on the foot board of a bed. However, because ofthe wide range of foot board sizes that must be accommodated, such hookseither have to be customized for certain foot boards, or else thesnugness and security of the fit must be compromised. Further backgroundand many other related references are known to those of skill in thisart.

[0009] Despite the:long history of technological developments of suchhousings and compression devices, man continues in his manifest pursuitof the ideal system which balances maximum therapeutic benefit withpracticality and patient comfort.

[0010] Many other problems, obstacles and deficiencies faced in thesefields and/or addressed by the present invention will be apparent tothose skilled in that art, especially in light of the furtherdescriptions herein.

SUMMARY OF THE INVENTION

[0011] It is a primary object of the present invention to provide a newand improved cyclic compression system which overcomes the problems anddeficiencies of the prior art.

[0012] It is also an object of the present invention to provide a novelhousing which can be conveniently handled and simply but securelymounted to a hospital bed or the like. Another object of the inventionis to produce a simple, compact, inexpensive pump and housing which arecapable of yielding substantial therapeutic and prophylactic benefitsdespite their small size and simplicity.

[0013] The present invention is directed toward accomplishing suchobjects and others and improving upon the teachings of the prior art byuniquely combining. refining and modifying various concepts and featuresto provide a significant advancement in the field. A primary object ofthe invention is to provide a small, lightweight and comfortable butdurable device which helps prevent and/or solve many of the problemsassociated with impaired or poor circulation.

[0014] Another object includes providing a pneumatic device of simpleconstruction which encloses as much of the foot as possible in order tosqueeze as much of the foot as possible. Particularly it is an object toenclose those portions which may be readily compressed to improvecirculation while allowing other less compressible portions to be opento the air. Still other objects include providing comfort and moisturecontrol and avoiding the need for accessories such as additionalstockings, wraps, sandals, straps, and the like, which have beenrequired by the prior art.

[0015] Another object of the present invention is to provide anintermittent compression device requiring a minimum volume of air perpulsation.

[0016] Another object is to provide a blood circulation aid which willfit a wide variety of patients without requiring any modification oradjustments

[0017] Another object of the present invention is to provide adisposable device of simple construction which is of a universal shapein that it can be applied to either the left or the right foot with thesame effect.

[0018] Another object is to provide a device of great simplicity andease-of-use in contrast to other devices designed for the purpose ofaiding blood flow in the feet and legs. Related objects includeproviding a lightweight, simple article that can be easily and quicklyapplied to the foot while still achieving the other objects of theinvention.

[0019] Another object of the invention is to provide a blood flowimprovement device which, due to its inherent low manufacturing cost, ispractical to use as a disposable item rather than cleaning and reusing.

[0020] Still another object is to provide a cyclic compression devicewhich achieves optimum compression and optimum blood flow enhancement ina manner that minimizes anxiety and discomfort to the patient.

[0021] Other objects relate to the convenience of the product. It isdesired to provide a complete system that can be hand carried to thepatient and easily and securely deployed without concern aboutcompatibility with the bed on which the product is to be deployed. Acompact, easily-stored and minimally-obtrusive product is also sought.

[0022] The present invention addresses the foregoing and many otherobjects by providing an ingenious article that integrates a compressionbladder and its entire mounting, stabilizing and adjustment systems intoa simple and economical construction coupled with a control system andhousing that greatly surpass prior devices both in utility andingenuity.

[0023] The present invention will typically comprise a foot wrap devicemade from two sheets of fabric sewn or welded together to form aninflatable pocket or bladder that preferably constitutes as much of thedevice as possible without creating a bladder that is too uncomfortableor too large to be adequately inflated. One aspect of the inventionrelates to the roughly T-shaped or L-shaped configuration of its footwrap, with at least one portion or segment wrapping around the bottom ofthe foot and a second portion or segment wrapping around the back of theheel and ankle regions of the lower leg. As will be described withreference to the preferred embodiments, the invention may includevarious extensions or tabs provided to operatively join with otherextensions, tabs or the like, as may be beneficial for comfort andefficacy. In the preferred embodiments, both inner and outer fabriclayers are cut from the same pattern.

[0024] Fasteners formed integral with the extensions enable releasableapplication on the foot. Preferably, such fasteners include Velcro hookconnectors, and the outer surface of the foot wrap is formed of Velcroloop material (or the equivalent) for mating with the hook connectors.The inner layer of the foot wrap is preferably a vapor permeablematerial having greater elasticity than the outer layer. Both fabricsare preferably impermeable to air and capable of being fused together byheat welding or the like. A filling tube may be sealed into theinflatable bladder or pocket through the outer fabric layer.

[0025] In the first embodiment, the complete foot wrap weighs only afew, ounces and is soft and pliable. When it is properly applied, afirst dimpled or segmented portion of the inflatable bladder wrapsaround the main part of the foot and fastens to itself. Another portionis joined integrally in fluid communication with the first but wrapsaround behind the heel and ankle regions of the lower leg. The secondportion fastens to the outside surface of either itself or the otherportion. Thus, the foot is almost completely enclosed and surrounded bythe inflatable bladder, and the device securely holds itself in place onthe foot in order to compress as much of the foot as feasible when thebladder is inflated.

[0026] Fluid for such inflation may be supplied by one of the pumpsystems well known in the art, although the preferred embodimentincludes and provides several advancements over that art. The preferredembodiment includes a pump that operates in a pulsed sequence that canbe adjusted for any desired frequency and intensity according to theprescribed treatment. Preferably the pump/control is set to compress thefoot to pressures in the range between 120 and 190 mm Hg and to hold itin that pressure range for two seconds every fifteen seconds. Thispressure range is generally accepted by Applicant to ensure closure ofthe veins in the foot, although lower pressures may be partiallyeffective as well.

[0027] The preferred embodiments uniquely integrate more fundamentalaspects of the invention together with cushioning means for minimizinglocalized pressure concentrations acting on the foot, thereby inhibitingskin breakdown on the foot, especially its most vulnerable areas.Optimum compression of the foot is ensured by. enclosing as much of thesqueezable portion of the foot as is feasible. In the first embodiment,the inner and outer sheets are joined together at circular portions inthe interior of its inflatable bladder to help prevent excessiveinflation, particularly over regions of the foot that are lesscompressible. This further optimizes compression of the foot to ensureoptimum blood flow enhancement. Holes may be provided through the wrapat those circular portions to further enhance breathability of thepatient's skin.

[0028] The present invention also includes a unique pressure source forsupplying pressure to the referenced foot wraps. Pressure feedbackcontrol of the pressure supplied by the pressure source is provided evenduring the then-current compression cycle. The feedback system overcomessome of the difficulties inherent in its objects by incorporating spikeeliminators, as well as error detection means for alarming the operatorof error conditions such as kinked hoses or disconnected foot wraps. Thespike eliminator may include an accumulator, possibly in combinationwith a flow restrictor. The accumulator and restrictor are configured ina way that helps prevent the pressure sensors from over-responding toinitial surges of line pressure. Such surges are otherwise common closeto the pressure source with compression devices that provide quickinflation.

[0029] More particularly, the pressure sensing and control system mayinclude a transducer, an analog-to-digital converter, and a digitalmicro-controller that controls a plurality of solenoid valves to adjustthe supplied pressure in accordance with operator settings. Themicro-controller is interfaced through an operator console having aliquid crystal display and programmable keys to enter operator settings,which are then stored using various memory devices includingelectronically erasable programmable read only memory.

[0030] The combination of all the foregoing in an operative system isthought to be very beneficial, especially packaged in a housing that canbe releasably mounted on the foot board of a standard hospital bed bymeans of a pair of opposite, retractable mounting hooks having slopedsurfaces for biasing the source toward said foot board and having knobsat the distal ends thereof for helping retain the hooks on the footboard.

[0031] Numerous other features, advantages, and objects of the inventionare set forth and will be evident from the following more detaileddescriptions of certain preferred embodiments, particularly whenconsidered in light of the prior art together with the accompanyingdrawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Presently preferred embodiments constructed according to theteachings of the present invention are hereinafter described in moredetail. To those of ordinary skill in the art, the invention will becomemore readily understood from the specifications of those embodiments,particularly when considered in light of the appended claims and withfurther reference to the accompanying drawings, wherein like numeralsrefer to like elements throughout, and wherein:

[0033]FIG. 1 shows a perspective view of the basic elements of one ofthe presently preferred embodiments.

[0034]FIG. 2 shows the outer surface of one of the foot wraps 1Apictured in FIG. 1 as it is laid out flat.

[0035]FIG. 3 shows a view of the inner surface of the foot wrap 1A laidflat.

[0036]FIG. 4 shows a top view of the foot wrap 1A in place on a humanfoot.

[0037]FIG. 5 shows a side view of the foot wrap 1A in place on a humanfoot.

[0038]FIG. 6 shows an end-on view of the foot wrap 1A as it is laid outflat with its bladder 9 shown deflated, the view being from the end thatis oriented at the top in FIG. 2.

[0039]FIG. 7A shows a cross-sectional view from the opposite directionof FIG. 6, the section line “7A-7A” being shown in FIG. 3 and bladder 9being shown inflated in FIG. 7A.

[0040]FIG. 7B shows a second cross-section of the foot wrap 1A,sectioned along plane “7B-7B” shown in FIG. 2, with its bladder 9 showndeflated.

[0041] FIGS. 8A-8D illustrate the manner of operatively applying a footwrap 1A to a foot 100.

[0042]FIG. 9 shows a schematic layout of the electrical and pneumaticsystems of the preferred embodiment shown in FIG. 1.

[0043] FIGS. 10-12 show flow charts which characterize the operation ofthe preferred embodiment shown in FIG. 1.

[0044]FIG. 13 shows a top view of the preferred embodiment's pumphousing 20, which also functions as a carrying case and as a means formounting the pump on the foot board of a hospital bed or the like.

[0045]FIG. 14 shows a front elevation view of the pump housing 20.without certain details.

[0046]FIG. 15 shows a rear elevation view of the pump housing 20.

[0047]FIG. 16 shows a bottom view of the pump housing 20.

[0048]FIG. 17 shows a left side elevation view of the pump housing 20,with retractable mounting hooks 21 in their fully retracted position asin FIGS. 13-16.

[0049]FIG. 18 shows the left side elevation view of FIG. 17, except thatthe retractable mounting hooks 21 are in their fully extended positionin FIG. 18, as also pictured in FIG. 1.

[0050]FIG. 19 shows an exploded view of the rear portion of pump 20.

[0051]FIG. 20 shows an exploded view of the front portion of pump 20,illustrating many of the particular embodiments and relativeconfigurations of the components schematically shown in FIG. 9.

[0052] FIGS. 21-23 show alternative embodiments to the foot wrap 1Ashown in FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] Referring to FIG. 1 of the drawings, there is shown an isometricperspective view of the basic elements of the presently preferredembodiment. That embodiment, referred to as cyclic compression system500, basically comprises a pump unit 501, two foot wraps 1A & 1B, powercord 24, and connecting hoses 30A and 30B. In many respects thatembodiment is intended to be substantially identical to a product knownin the marketplace as the “PlexiPulse” unit manufactured by ApplicantKinetic Concepts, Inc., San Antonio, Tex. The “PlexiPulse” unit is nowavailable to customers of NuTech, which is affiliated with KineticConcepts, Inc., and also has offices in San Antonio, Tex. Although thefollowing description is intended to be complete within itself and withreference to its corresponding Co-Pending Application (referred topreviously), further reference to said PlexiPulse unit may furtherenrble those of ordinary skill in the art to make and use the inventionshereof.

[0054] The pump unit 501, which is AC-powered via a conventional powercord 24, operates to cyclically inflate and deflate bladders 9A and 9Bformed in foot wraps 1A and 1B, respectively, to intermittently compressthe foot. The unit is described most particularly for application on thefoot, as many aspects of the invention can be appreciated there.Nonetheless, regardless whether it is mounted on a patient's calf, foot,hand, or any other part of the body (especially those containing veinsthat can be emptied by compression), such intermittent compression maybe beneficial for a wide variety of indications. Among others, the knownmedical indications include the following: venous stasis, poorcirculation, post-operative pain and swelling, edema, cutaneousulceration, and elevated compartmental pressures. It may also serve toprevent deep vein thrombosis and reduce wound healing times. Moreparticular aspects of preferred operation of the system 500 will bedescribed further herein.

[0055] For purposes of this description, reference may be made to“upper”, “lower”, “forward”, “backward”, “left”, “right” and“horizontal” features when referring to certain drawings. Suchreferences and others like them are made principally to render thedescription more easily understood in view of the orientations in thedrawings and in view of a reference orientation of system 500 or itssubject. As will be evident to those of ordinary skill in the art, suchorientations are not necessarily maintained throughout the operation ofthe described embodiments, much less would they necessarily be requiredfor utilization of the invention.

[0056] Referring to FIGS. 2-7, foot wrap 1A is shown, first laid flatand then in relation to a foot (designated as foot 100 in the drawings)during normal operation. Foot wrap 1A is preferably identical to footwrap 1B (shown in FIGS. 1 and 9) and thus has parts which are numberedthe same as in the other figures, except that the “A” and “B”designations may be used to distinguish various parts of wrap 1A fromsimilar parts of wrap 1B, respectively. Variations in the shape of footwrap 1A may be made to some degree, with commensurate sacrifices in (orenhancement of) the benefits of the invention. The angle of the inlet 11relative to the foot wrap 1A, for instance, may be varied from one footwrap to the next without much effect on its operation. The inlet anglepictured in FIG. 1 is considered most advantageous, tending to bias hose30A in a direction for avoiding kinking of that hose 30A. Thedescriptions of foot wrap 1A are equally applicable to foot wrap 1B. Oneaspect of the invention is that the shape of wrap 1A renders ituniversal in that it is thought to be applicable to either foot withoutsignificantly affecting its efficacy. As will be evident, though, thefoot wrap 1B could be made as a mirror image of its counterpart 1A. Thesimplicity of the shape also allows for the wrap 1A to fit on other bodyportions as well even though it is ideally suited for the foot.

[0057] In FIG. 2, foot wrap 1A is shown open (i.e., laid out flat), Withthe cuter surface of foot wrap 1A facing the viewer. FIG. 3 is a viewfrom the opposite side showing the inner surface of foot wrap IA. FIGS.6-7B show various views that generally illustrate the construction ofthe foot wrap. The foot wrap 1A is generally formed of two sheets 2 and3 which are bonded together to form a bladder 9 with tabs 4-7 extendinggenerally away from each other. Foot wrap 1A also includes a fluid inlet11 (also referred to as “fitting 11”) for inflating and deflating thebladder 9, as well as faster 8 and 88 for releasably securing the wrap1A on a foot 100. These basic components (and others) of wrap 1A arereadily available through numerous manufacturers.

[0058] Referring primarily to FIG. 7B, sheet 2 is preferably cut from arobust, non-stretch fabric. The outer surface of sheet 2 (i.e., thesurface facing away from sheet 3) has loops like those found on Velcroloop material, which are compatible to releasably engage Velcro hookmaterial. The interior surface of sheet 2 (i.e., the surface facingtoward sheet 3) is heat-weldable so that it can be joined to sheet 3.Sheet 2 is laminated with polyurethane in a conventional manner, to sealit and render it RF-weldable. Sheet 2, thus, is referred to as a sheetof laminated loop fabric that forms the outer sheet of wrap 1A. In thepresently preferred embodiment, sheet 2 is a Velcro-compatible,continuous-loop nylon fabric manufactured by Guilford, USA and availableunder the trade designation “Tricot”.

[0059] Preferably, although each of the sheets 2 and 3 are airimpermeable, they are each also formed of vapor permeable fabric. Othercommercially-available fabrics, such as that marketed as low air loss“GoreTex” by the W. L. Gore Company, have long been known to providesimilar benefits in other contexts. Their vapor-permeability serves toenable moisture from foot 100 to evaporate despite the foot wrap 1A.This is especially preferable for sheet 3 so that perspiration adjacentbladdar 9 can be evacuated from the site by the fluid that inflatesbladder 9. The removal of surface moisture forming on the patient's skinbeneath the foot wrap is beneficial since it helps promote themaintenance and healing of skin conditions, especially during prolongeduse. As will be evident to those skilled in the art, however, someaspects of this invention can still be appreciated with materials ofmore limited porosity, generally so long as foot wraps 1A and 1B remaininflatable.

[0060] Sheet 3 is preferably cut from the same or a similar pattern assheet 2, so that it matches neatly with sheet 2. The manufacturingprocess may be simplified by simultaneously die-cutting the sheets 2 and3, and then joining the border and appropriate other locations of eachsheet to the other (as described elsewhere herein). The cutting processmay also be simplified by welding the two sheets together whilesimultaneously heat-cutting the border of the fabric with the same die(as is common in the art with tear-and-seal dies), although this processmay not always be successful due to the compositions of the sheets.

[0061] Sheet 3 is preferably also an elastic fabric, so that it expandsmore than outer sheet 2 when bladder 9 is inflated. The inner surface ofsheet 3 (i.e., the surface facing toward sheet 2) is laminated withpolyurethane, thereby sealing it and rendering it heat-weldable toenable bonding with the inner surface of sheet 2. It is important thatthe outer surface of sheet 3 (i.e., the surface facing away from sheet2) is soft and comfortable against the skin, as that surface is likelyto be in contact with the patient's skin during use. In the preferredembodiment, sheet 3 is a laminated lycra material that meets theforegoing characteristics.

[0062] As will be evident from this description to those of ordinaryskill in the art, other fabrics may be substituted for the preferredfabrics of sheets 2 and 3 with related sacrifices of various aspects ofthis invention. Less costly, substantially inelastic nylon fabrics couldbe used for both sheets 2 and 3 while still appreciating therapeuticvalue of the foot wraps 1A and 1B. Similarly, stitching or adhesivescould be used rather than the more beneficial RF welding, and somebenefits could still be appreciated with a PVC-like composition made ofsheets appropriately welded together.

[0063] Preferably, bladder 9 is formed between sheet 2 and sheet 3 byweld line 10. Weld line 10 is a closed line so that it completelysurrounds and thereby defines a closed area on each of sheets 2 and 3.Thus, bladder 9 is a sealed bladder, the only inlet or outlet of whichis provided by the tubular connector fitting 11 (described below).Bladder 9 is provided in foot wrap 1A to apply pressure on the foot 100when the wrap 1A is secured on the foot 100 and the bladder is theninflated. Bladder 9 is primarily intended for pneumatic inflation,although fluids other than air could be substituted by those of ordinaryskill in the art. Although bladder 9 would be of minimum size and volumeconsistent with its object of exerting compression pressure on the footwhile requiring a minimum volume of pressurized air per pulse (asachieved by bladder 509 shown in the alternative embodiment of FIG. 21),Applicant believes that similar pressures distributed over more of thefoot provides a greater benefit for the patient. Thus, bladder 9 of footwrap 1A extends over most of the entire surface area of wrap 1A tooverlap and enclose as much of the portions of the foot which containsignificant veins as is feasible. Although bladder 9 in the preferredembodiment may not compress the veins in the toes of most patients, itis of sufficient size to compress virtually all other regions of thefoot, except the most distal portion of the heels, which are thought tocontain few significant veins for compression purposes.

[0064] In contrast, it can be seen with reference to FIG. 21 thatbladder 509 occupies only the central sole area of the foot 100.Pressure and bladder expansion there causes the fabric enclosure aroundthe foot to tighten and distribute limited compression forces aroundother portions of the foot 100 as well. In the embodiment of FIG. 21,bladder 509 is circular, roughly 3 to 5 inches in diameter. However,other shapes of bladders may be substituted to employ many of the otheraspects of the invention. For instance, FIGS. 22 and 23 show two otheralternative embodiments to the foot wrap 1A shown in FIG. 3. FIG. 22,specifically, shows a T-shaped foot wrap 401 having a similarly T-shapedbladder 409 which is capable of enclosing much of foot 100, with somelimitations. The differences between the shape of bladder 9 and bladder409 ensure more complete enclosure of vein-containing portions bybladder 9, as well as enable its universal characteristics (referencedpreviously). In the opposite direction from the smaller shape of bladder409 is bladder 609 shown in FIG. 23, which further ensures completeenclosure and compression of the vein-containing portions of foot 100,while also further ensuring a secure attachment to foot 100. Othervariations and details are described in said Co-Pending Application andat least one other application referenced and incorporated therein.

[0065] Each of the embodiments shown in FIGS. 21-23 are constructed andused essentially using the same methods and materials as with the FIG. 3embodiment, except as otherwise noted. Accordingly, like (or related)aspects of these various embodiments are numbered similarly. Forinstance, each embodiment has a strap that is positioned to be securedaround the back of the leg of a person on which it is to be used. Therespective straps are numbered 7, 507, 407 and 607, for FIGS. 3, 21, 22,and 23, respectively. The differences from the embodiment of FIG. 3 andthose of FIGS. 21-23 will be fairly evident from a comparison of thosefigures.

[0066] The principal difference between the FIG. 3 embodiment and thatof FIG. 21 relates to the size of the bladder. In attempts to render thewrap 1A more comfortable and more likely to ensure against skinbreakdown, Applicant has found that by increasing the size of bladder 9to that shown in FIG. 2, the resulting blood flow is improved. Althoughthe findings are still preliminary, compressing more of the foot notonly renders the wrap 9 more comfortable, but informal venogram studiesindicate that greater surges of blood flow tend to be produced bycompressing more of the foot. The same informal studies also suggestthat the placement of circular welds 53-56 in the interior of bladder 9further enhances blood flow. That cushioning effect is believed to helpinhibit the breakdown of skin that might otherwise be associated withstraps 507, 407 and 607—particularly breakdown created by stressconcentrations on strap 407 and the skin around the rearward ankle areaof foot 100. As is also true to some degree for the embodiment of FIG.2, the embodiment shown in FIG. 22 is provided with means for cushioningthe leg strap 407.

[0067] Wrap 401 achieves the cushion in part by having a foam strap 407that is inherently cushioned and in part by extending its inflatablebladder along the length of the strap 507. Wrap 1A, in contrast, onlyachieves the cushion by extending its inflatable bladder 9 along thelength of its strap 7. Foam strap 407 is an elongated patch of foammaterial that is secured to strap 407 in an orientation coincident withthe length of strap 407. The cushion foam used in the preferredembodiments of the embodiments shown in FIGS. 21-23 is commerciallyavailable in the U.S. under the trademark “Vel-Foam”, although othercushion material could also be used. Securing the foam 407 to the restof foot wrap 401 may be accomplished either by a variety of conventionalmeans, such as by stitching, glue, or heat-welded lamination. Ifstitching is to be used, the stitching is preferably done at a locationof the Wrap that is not inflatable, thereby avoiding leaks in theinflatable bladder. For instance. the Vel-Foam strap 407 is shownstitched on three sides to the remainder of wrap 401 with stitching 419in a narrow region outside weld 410 that defines bladder 409. Vel-Foampatch 418 must be stitched around only three of its four edges(excluding edge 418′) in order to avoid creating an air leak in bladder409. Therefore it may be preferable to glue patch 418 in place usingconventional glues used by seamstresses for lasting application.

[0068] Heat-welded circular recesses 417 are preferably spaced onbladder 409 to minimize billowing (excessive bulging) of bladder 409when it is inflated. Such circular recesses are best positioned atlocations likely to overly bonier (or less compressible) areas of foot100.

[0069] Many other features of the embodiments shown in FIGS. 21-23 willbe evident to those of ordinary skill in the art in view of the otherteachings herein, and in view of the prior art.

[0070] The preferred shape of wrap 9 is unique and advantageous. Wrap 9as a whole may be referred to as T-shaped, J-shaped or L-shapeddepending on which elements are focused upon. For simplicity inreference, it will simply be referred to as a “convoluted J-shape”. Theconvoluted J-shape of wrap 1A has four basic extensions—referred to astabs 4-7.

[0071] Tabs 4-7 are oriented to ideally secure wrap 1A to the foot 100of the patient. As can be seen with reference to FIGS. 2-7, the heeledge 6′ that spans between tab 6 and tab 7 is concave and has agenerally circular curve for surrounding the heel 102 of foot 100. Onceso wrapped to encircle the heel 102 of foot 100, Velcro connector 8 atthe distal end of tab 7 is naturally oriented to overlap and secureitself to the outer surface of sheet 2 of tab 6. The toe edge 4′ is alsocurved concavely, although only to a slight degree, to encircle the toeregion 103 of the foot 100. Once so encircling the toe region of thefoot, Velcro connector 88 overlaps and engages the outer surface ofsheet 2 of tab 4. The size of Velcro tabs 8 and 88 should be determinedbased on the degree of closure desired, which is dependent, at least inpart, upon the types of Velcro materials used. Prior teachings havesuggested that Velcro connectors on compression devices should be smallenough to allow for release in the event of over-pressurizing aninflatable compression device; however, Applicant gives limited credenceto such teachings and has found that larger tabs may be desired in orderto ensure secure enclosure of the foot in normal operation. Sizeincreases of tabs 8 and 88, though, should be balanced against desirenot to have Velcro hock connectors overlapping to a degree that wouldengage the skin of foot 100. Specifically, Applicant, in alternativeembodiments (not shown), has utilized larger Velcro hook connectors atthe location of Velcro hook connector 88 in FIG. 2, and has found thatthe width of tab 5 can be increased to accommodate such larger Velcroconnectors.

[0072] As is evident in FIG. 2, the orientation of tab 5 issubstantially perpendicular to the orientation of tab 7. Similarly, tabs4 and 6 extend in directions generally perpendicular to one another,although tabs 4 and 6 are more rounded at their distal ends 4″ and 6″than are tabs 5 and 7. The distal ends 4″ and 6″ of tabs 4 and 6 areinflatable in the preferred embodiments; whereas the distal ends 5″ and7″ of tabs 5 and 7 are not inflatable and are provided with Velcroconnectors 8 and 88 stitched thereto, respectively. Distal ends 5″ and8″ are also considered squared relative to the more rounded ends 4″ and6″. In use, the uppermost edge of wrap 1A is provided by edge 5′ whichspans between tabs 5 and 7. Unlike each of the other edges, 5′, 6′ and8′ that span between tabs 4-7, edge 4′(spanning between the distal ends4″ and 6″) has a convex shape, although only slightly so. The inflatableends 4″ and 6″ of tabs 4 and 6 are also convex, although more so thanedge 4′.

[0073] A blank (i.e., non-inflatable) central portion 5′″ is provided atthe proximal end of tab 5, in the part of wrap 1A spanning between weld10 and connector 88. The purpose of blank central portion 5′″ for tab 5is to ensure that connector 88 adequately overlaps tab 4 on varyingsizes of feet (thereby ensuring against contact between the Velcro hooksof connector 88 and the skin of foot 100), while also limiting the sizeof bladder 9 by not extending it over blank central portion 5′″. Thebalance was drawn principally because the tab 5 is sized such that blankcentral portion 5′″ will overlap tab 4 (which is already inflatable) inmost applications. The position of inflatable extension 7 is orientedrelative to the rest of wrap 9 to wrap around more or thevein-containing portions of a patient's lower leg, as opposed to rightaround the back of the heel 102 and ankle 104 of leg 105.

[0074] Referring especially to FIGS. 1, 6 & 7, fitting 11 is a tubularfluid connector having an elbow form to reduce the extent of protrusionfrom sheet 2. Its elbow shape also enables connection of a fluid hose30A (shown in FIG. 1) to the fitting 11 and helps minimize thepossibility of kinking hose 30A during use. A conventional, barbed hoseconnector 18 is incorporated in the outermost end of fitting 11 toenable connection with hose 30A, although a properly sized hose 30Acould also be connected merely by a friction fit with fitting 11.Fitting 11 is formed of a compatible heat-weldable material and has abase flange 12. This fitting is inserted from the inside of sheet 2through a hole 12′ punched in fabric sheet 2 and is then positioned sothat flange 12 contacts the heat-weldable inner surface of fabric sheet2. The engagement between flange 12 and sheet 2 is then weldedfluid-tight to completely seal the bladder 9A from leakage.

[0075] As suggested above, tabs (or “extensions”) 4-7 extend generallyaway from each other. With wrap 1A laid flat, tabs 5 and 4 lie onopposite sides of wrap 1A, extending generally along the line “7A-7A” inFIG. 3. Extension or tab 7 of foot wrap 1A lies substantiallyperpendicular to line “7A-7A” and is considerably longer than tab 5. Inother embodiments (not shown), tab 7 is less perpendicular than picturedin FIGS. 2-7. Hook connector patches 8 and 88 are sewn or welded at ornear the distal ends of 5″ and 8″ tabs 5 and 7, respectively, on theouter surface of inner sheet 3.

[0076] As shown best in FIGS. 2 and 3, the convoluted J-shape of bladder9 includes circular recesses 53-56 in the midst of bladder 9. Suchrecesses 53-56 combine with other features of bladder 9 to optimizecompression of foot 100. Particularly, recesses 53-56 are oriented tominimize excessive billowing of bladder 9, particularly over the lesscompressible areas of each lateral side of foot 100. Inflatable tabs 4and 6 remain inflatable despite recesses 53-56 to provide compression ofother regions of the foot. The preferred positions and orientations ofrecesses 53-56 are best evident in the FIGS. 2 and 3 of the drawings.

[0077] In part by weld 10 and elsewhere by welds 10, the outer perimeter14 of the entire foot wrap 1A is RF-welded to join sheets 2 and 3,thereby forming a composite fabric wrap 1A with the single tubularfitting 11 mounted therein. Such simplicity is in striking contrast tothe large and complex foot wraps heretofore employed for similarpurposes. This preferred embodiment weighs less than 6 ounces and isapproximately 38 centimeters in the direction of line “7A-7A” of FIG. 2by 39 ½ centimeters in the perpendicular direction of line “7B-7B”.Other forms of connecting the sheets may be used, such as by stitching,although commensurate sacrifices of inventive aspects will probably beassociated with such a change.

[0078] Referring to FIGS. 8A-8D, foot wrap 1A also stands out for itsease and simplicity of use. First place the foot wrap in the flatposition shown in FIG. 8A and place the foot 100 over the centralportion of bladder 9. Foot 100 should be positioned on bladder 9 in away such that the center of heel 102 of foot 100 is positioned just offof bladder 9 and inside the arc of heel edge 6′. The length of foot 100should extend across bladder 9 in a direction parallel to the length oftab 7, in a path directly between circular welds 55 and 56, such thatthe foot lies in contact with inner sheet 3 of wrap 1A. Then, as in FIG.8B, wrap tab 4 and 6 around the foot 100, with tab 6 naturally followingand extending toward the back of the leg 105. Tab 4 should wrap over thetop of the foot 100. Then wrap tab 5 over tab 4 as in FIG. 8C, so tabs 4and 5 overlap on the top of the foot. Adjust the tightness of the fit tothe degree desired (preferably snug) and press the hook patch 88 of tab5 onto the outer surface of tab 4 so they form a secure connection.Then, to completely secure the bladder 9 to the foot 100, draw tab 7around the back of the foot 100 as shown in FIG. 8D and pull it snug.Hooked tip 8 (shown in FIG. 8A) is then pressed onto the outer surfacesof tab 6 where it overlaps on the side of the foot 100. The foot wrap 1Ais now locked in position until the fastenings 8 and 88 are peeled openfor removal of the foot wrap 1A. This procedure can be accomplished in afew seconds, and removal requires only pulling of the two tabs 5 and 7.

[0079] Minor adjustments in the preferred position of the bladder 9relative to the foot 100, if required, may include loosening andrepositioning one or both tabs 5 and 7 as necessary. The relativelengths of tabs 4, 5, 6 and 7 are not fixed but must meet therequirement of overlapping sufficiently to form a secure fastening whenwrapped around foot 100. Thus tab 4 may be shorter than tab 5, althoughthe general proportion illustrated in FIGS. 1-8 is preferred. The footwrap 1A will fit a wide range of foot sizes without change in theapplication technique. If necessary, feet of very small persons may befitted through the use of firm padding above the instep and behind theheel to simulate a larger foot while allowing the bladder to act againstthe sole of the foot through the padding.

[0080] The size and shape of the bladder 9 and foot wrap 1A in relationto foot 100 may also be larger than shown, even enclosing the entirefoot, while still appreciating many aspects of the invention. Althoughnot included in the pictured embodiments in view of the objects ofreducing complexity, size, weight and material cost, among others it ispreferred to provide a bladder which fully encloses the foot or, perhapsmore practically, extends to just enclose the toes of the feet. However,larger capacity pumps and/or slower cycle times must be employed withsuch alternative embodiments in order to compensate for the bladdershaving larger volumes.

[0081] Nonetheless, without encompassing the entire foot, air and footmoisture vapor can exchange between the foot and the foot wrap from boththe front and rear areas where the foot wrap 1A wraps onto the foot 100.Circular recesses 53-56 are also provided with holes 53′-56′ in thecentral portions thereof to provide for greater ventilation for the foot100. Such holes 53′-56′ may be punched, cut or die-cut central tocircular welds 53-56 in the same or similar manner to the formation ofthe outer perimeter 10′ of foot wrap 1A.

[0082] During the deflated phase of pumping, the fit is looser and aircan more easily diffuse the covered areas of skin beneath the foot wrap1A. With proper materials as in the preferred embodiment, such diffusionis not as critical though, because the material of sheet 3 is vaporpermeable—allowing moisture to vacate the skin surface through sheet 3.The soft inner surface of foot wrap 1A, which is also the outer surfaceof sheet 3, may be covered with a springy, open pile or other liningwhich promotes the entrance of air into the area between sheet 3 and thefoot 100 during the decompression phase. An alternative embodiment ofthe invention may use a non-vapor permeable sheet 3 having an outersurface with such air movement promoting characteristics.

[0083] This small, lightweight, inexpensive foot wrap 1A in itself issure to fill an important need in modern medicine. Nonetheless, as willbe evident from this description to those of ordinary skill in the art,many aspects of this invention may be appreciated with other compressiondevices, possibly in combination with other intermittent or sequentialcompression features or devices, and possibly employed on other parts ofthe body including the hand, the leg, the arm or combinationsthereof—naturally, with commensurate sacrifices of certain aspects ofthis present invention.

[0084] Referring again to FIG. 1, the housing 20 of unit 501 will bediscussed briefly. Housing 20 is an injection molded plastic housingthat comprises front housing plate 27 and back housing plate 26 fastenedtogether using any conventional means such as screws. Front housingplate 27 and back housing plate 26, once connected, form handle 23 whichfacilitates carrying of pump unit 501. The preferred embodiment's pumpunit 501 as a whole weighs roughly ten pounds, although the shape ofhousing 20 is ideal for units of any weight that can be safelyhand-carried and supported on the foot board or headboard of apatient-supporting bed. The components inside the pump unit 501 arepreferably arranged so the center of gravity for the pump unit 501 isroughly concentric with the volumetric centroid of the housing 20,although great care need not be taken in this as long as the center ofgravity is appreciably below the height where the hooks 21 rest on thefoot board 600. Such a location is preferred in order to distribute theweight of unit 501 between its two mounting hooks 21A and 21B and toensure the unit is not top-heavy, both for ease in carrying andstability in mounting. The shape of housing 20 and the relativepositioning of hooks 21A and 21B naturally help ensure that the centerof gravity is centrally located.

[0085] Referring still to FIG. 1 and also to FIG. 9, where more detailedfeatures of system 500 are shown schematically, power switch 66 turnsthe pump unit 501 (and thus the system 500 as a whole) on and off. Powercord 24 is a conventional power cord for providing standard 115/120volt, 60 Hz power to the pump unit 501. Preferably cord 24 is a hospitalgrade cord.

[0086] The links between pump unit 501 and foot wraps 1A and 1B areprincipally pneumatic. Right and left hose connectors 22A and 22B arethe female members of conventional quick-disconnect air line connectors.Connectors 22A & 22B are firmly secured to front plate 27 of housing 20to provide a connection inlet from foot pump housing 20 to therespective air hoses 30A and 30B of right and left foot wraps 1A and 1B.The ends of hoses 30A and 30B that connect to housing 20 are adaptedwith integral male connectors 31A & 31B for easy mating with connectors22A & 22B. Connection and disconnection of connectors 31A and 31B can bedone easily with one hand and little effort. The connections betweenhoses 30A & 30B and inlets 11A & 11B are completed with conventionalbarbed line connectors 18A and 18B. Connectors 1 8A and 18B providerelatively permanent, sealed connections for keeping the hoses 30 andwraps 1A & 1B integral.

[0087] Operator console 42 provides a user interface to themicroprocessor of unit 501, allowing the user to either enter individualsettings from a selection menu (discussed further herein) or selectdefault settings. Operator console 42 basically comprises an LCD (liquidcrystal display) assembly 46 formed in a membrane panel. LCD assembly 46comprises a two-line, twenty character alphanumeric liquid crystaldisplay which displays programming instructions, status updates, andalarm messages to the operator. The membrane panel of console 42 hasintegral switches 43-45 therein, namely: “PULSE ON/OFF” switch 43;operator selection switches 44A, 44B, 44C respectively designated “A”,“B” and “C”; and “OPTIONS” switch 45. As will be evident to those ofordinary skill in the art, other switch configurations and/or optionsmay be substituted within the scope of this invention. For instance, inone alternative embodiment the “PULSE ON/OFF” feature has beeneliminated and switch 43 has been dedicated to silence any alarms, withappropriate labeling of switch 43. To eliminate that feature, the system500 will always be in the air pulse therapy mode (see below) when thesystem is empowered, i.e. when main power switch 66 is ON.

[0088] The operation of system 500 is primarily controlled by theprimary processor of pump unit 501, which is micro-controller 41.Micro-controller 41 is a conventional type of control board. As will beevident to those of ordinary skill in the art, the specific charactersof micro-controller 41 are dictated by its intended operation, asdescribed and evident further herein and in said Co-Pending U.S.Application (and other references included therein).

[0089] PULSE ON/OFF switch 43 both selects and de-selects an air pulsetherapy mode for the system 500. If PULSE ON/OFF switch 43 is depressedto its ON state when the main power switch 66 is Off, the system 500remains inoperative, but if PULSE ON/OFF switch 43 is depressed ON whenthe main power switch is ON, the controller of system 500 causesdelivery of pneumatic pulses to the foot wraps 1A and 1B according tothe currently set operating parameters. When system 500 is turned on,such parameters are preset to default to the last entered parameters,but they can be adjusted at any time thereafter by appropriate selectionof the OPTIONS switch 45 and operator selection switches 44A-C when themain power switch 66 is ON, regardless whether switch 43 is actuated.Turning the PULSE ON/OFF switch 43 OFF during operation will turn offcompression/decompression cycling.

[0090] The remaining basic components of pump unit 501 are shownschematically in FIG. 9, including without limitation: GPDU PowerDistribution Board 49, power supply board 51, and air control board 50.On the pneumatic side, the unit 501 basically includes: compressor 38,compressor cooling fan 36, accumulator 37, two normally-closed inflationsolenoid valves 36A & 36B, two normally-opened deflation splenoid valves32A & 32B, manifold 35, air hoses therebetween, and various other lessercomponents which will be clear from the drawings, particularly in viewof the following more detailed descriptions of the operation of system500.

[0091] The operating protocol of operator console 42 will now bedescribed. When the main power switch 66 for the system 500 is firstturned ON, the micro-controller 41 (FIG. 9) displays a query on the topline of LCD assembly 46 requesting the operator to indicate whetherthere is a new patient. The bottom line of LCD assembly 46 displays thechoices “YES” or “NO” above operator selection switches 44A or 44B,respectively. Upon selection of “YES” by depressing switch 44A, theoperator has 5 seconds to depress OPTIONS switch 45 (discussed herein).Otherwise, micro-controller 41 automatically stores the default valuesfor the pump's settings (discussed herein) from ROM 52 into RAM 47 (seeFIG. 9). A selection of “NO” or no selection within 30 seconds causesmicro-controller 41 to retrieve from the power down memory (discussedherein) the settings stored in memory when the unit was last poweredoff.

[0092] A depression of “YES” followed by a depression of OPTIONS switch45 displays for user selection the first configuration (or “menu”)option (see Table 1) on the top line of LCD assembly 46. Each subsequentdepression of OPTIONS switch 45 sequentially displays a differentconfiguration option for selection by the user (see Table 1). The bottomline of LCD assembly 46 simultaneously displays a selection of up tothree choices for the configuration option displayed in the lineimmediately above. Those choices are displayed spaced across the secondline of LCD assembly 46 with each choice centered above a correspondingoperator selection “programming” switch 44A-44C. The operator enters achoice by depressing the operator selection switch 44A, 44B, or 44C thatis directly beneath the appropriate display corresponding to the desiredselection. Depression of operator selection switches 44A-44Cappropriately signals micro-controller 41 to select the specified choiceor query the operator for additional information. Therefore, byprogressing through the display “option” menus and selecting the desiredoption parameters, the system operator may program all the optionsrequired for use during the operating session. However, if defaultvalues are selected, (note that values are always stored in power downmemory) the default settings preferably are: both feet selected, cycletime 15 seconds, hold time 2seconds, and left and right pressure levelsof 150 mm Hg. Other default combinations, such as 150 mm Hg on both feetfor a 3-second hold, with a 20-second cycle time have also been usedwith favorable results.

[0093] Table 1 discloses the menu selection options and the parametersavailable for use in the preferred embodiment of the present invention.Whenever the option selection process is complete, and whenever the“HOME” option is selected, the LCD display returns to one of three HOMEdisplays as appropriate. The three HOME displays on the first line are:“Left and Right Pulse ON”, “Left Only-Pulse ON”, and “Right Only-PulseON”. The second line of each HOME display has only oneoption—“(OFF)”—positioned above switch 44C. Selection of “(OFF)”deactivates the foot compression features of system 500 and the “ON” and“(OFF)” LCD displays are changed to “OFF” and “(ON)”, respectively.TABLE 1 MENU SELECTION OPTIONS IN THE ORDER DISPLAYED Option DescriptionFoot Pulse Select Displays and allows the operator to select either oneor both feet for pulse therapy. Cycle Time Adjust? “DECR INCR HOME”allows the operator to select the foot pump's cycle time; when both feetare selected, cycle time is total time required for foot wraps 1A and 1B(see Figure 9) to sequentially inflate, hold, and deflate; cycle timesrange from 10 to 60 seconds, user selectable in 10 second intervals.Hold Time Adjust? “DECR INCR HOME” permits the operator to adjust theamount of time that the pressure is maintained in the respective footwrap after inflation occurs; selections are 1, 2, 3, 4, and 5 seconds.Left Foot Pressure Adjust? “DECR INCR HOME” permits the user to adjustthe foot pressure level in the left foot wrap from levels 2 through 10.Right Foot Pressure Adjust? “DECR INCR HOME” permits the user to adjustthe pressure level in the right foot wrap from levels 2 through 10. ViewTimers? “LEFT RIGHT HOME” allows the operator to view the foot pump'stotal therapy and operating times (Note that left and right foot therapytimes are individually displayed). For Service Use Only used bymaintenance personnel to calibrate the foot pump.

[0094] The pressure levels corresponding to the range of levels 2 to 10in the first embodiment are roughly 25-200mm Hg, although changes may beimplemented within the scope of this invention. For instance, onealternative would be to change the selectable range to 1-5,corresponding to actual pressures from 120 to 190 mm Hg. For thepurposes of disclosure, the timing and pressure setting ranges alongwith the system default settings of the preferred embodiment of thepresent invention have been described. The variability of such settingsis highly beneficial. However, one of ordinary skill in the art willreadily recognize that other ranges and default settings could besubstituted.

[0095] Referring to both FIGS. 9 and 20, the preferred system componentconfiguration and operation will be discussed in more detail. Foot wraps1A and 1B, designed to be securely fastened to a human foot, areconstructed from two sheets of fabric sewn or welded together to form aninflatable bladder 9 (described above). Alternative compression deviceswhich are known in the art (such as compression sleeves or gloves) alsocould be used to appreciate many aspects of the invention.

[0096] Power cord 24 delivers the overall system power supplied from thestandard 115V/120V, 60 Hz source to GPDU power distribution board 49and, in turn, to Power supply board 51. Power supply 51 converts thestandard 115V/120V AC to 12V DC and supplies the 12V DC back to powerdistribution board 49. Power distribution board 49 distributes the115V/120V AC and the 12V DC to each component according to theelectrical lines pictured in FIG. 9 and according to each particularcomponent's power requirements.

[0097] Compressor 38 provides the compressed air which is necessary toinflate the inflatable bladders 9A and 9B formed in foot wraps 1A and1B. Accumulator 37 stores the compressed air generated by compressor 38before delivery to foot wraps 1A and 1B. Micro-controller 41 polls PULSEON/OFF switch 43 to determine when compressor 38 should be turned on oroff. In the presently preferred embodiment. the compressor is alwaysrunning. When the pressure in accumulator 37 reaches its maximum,compressor 38 simply turns the air without being capable of pumping it.Nonetheless, the system 500 could be modified such that the pressurerequirements of the system factor in determining the operation ofsolenoid valves 32 and 36. Compressor 38 is turned on and off with thesystem 500 as a whole by actuation of switch 66. Fan 36 also operates tocontinually supply a flow of air over compressor 38 to prevent it fromoverheating.

[0098] In operation of the preferred embodiment, the operator may selecteither the right foot, left foot, or both feet for foot pulse therapy.As described before, such a selection is enabled by micro-controller 41and console 46. If both feet are selected for therapy, foot wraps 1A and1B alternately inflate and deflate to provide pressure against apatient's foot. However, for the purposes of disclosure, only operationof the right foot wrap will be described. However, it is to beunderstood that the left foot wrap operates in the same manner. In thisdescription, the numeral designations “A” are sometimes left off thereference numerals in order to enable easier reading on either the leftor right foot wrap systems. Right solenoid valve 36A opens to inflateright foot wrap 1A by allowing air pressure from accumulator 37 to bedirected into manifold 35. Manifold 35 simultaneously directs that airpressure to each of: (a) right foot wrap 1A via hose 28A, quick connect22A, and external hose 30A (shown best in FIG. 1); (b) right ventsolenoid valve 32A; and (c) right foot wrap pressure sensor 40A viasensor hose 29A, which has restrictor 34A and expansion tank 33A alongits course. While foot wrap 1A is being inflated (and thereafter throughthe hold time) to the selected or default pressure, right solenoid valve36A is held closed, thereby maintaining the air pressure in foot wrap1A. After the operator-selected or default hold time elapses, right ventsolenoid valve 32A opens, discharging the air from foot wrap 1A. Theabove cycle then repeats after the cycle time (i.e. the time betweeninflation) elapses.

[0099] The controller divides solenoid operation into four modes, asshown below: Pre-inflate Inflate Hold Deflate INFLATE OFF ON OFF OFFDEFLATE ON ON ON OFF

[0100] An initial surge of compressed air occurs when right solenoidvalve 36A is first opened. If right foot wrap pressure sensor 40Ameasures the initial surge of air, an erroneous pressure measurementwould occur. That is, right pressure sensor 40A would measure thepressure level as being much higher than it actually is in bladder 9A.To prevent right pressure sensor 40A from measuring such an initialpressure surge, the air flow path to right pressure sensor 40A containsright restrictor 34A and right expansion tank 33A. Right restrictor 34Arestricts the flow of compressed air into right expansion tank 33A, thusdecreasing the flow rate of the compressed air. Right expansion tank 33Aprovides an increased volume for expansion of the compressed air. As theinitial air surge expands into right expansion tank 33A, the airpressure decreases. Therefore, when right foot wrap pressure sensor 40Ameasures the initial surge of air pressure, that measurementapproximates the actual pressure being delivered from compressor 38 viaaccumulator 37 rather than the initial surge. Hence, the combination ofrestrictor 34A and tank 33A (and to an extent, each of themindividually) serve as means for eliminating spikes in the pressurefeedback sensed by sensor 40A.

[0101] Right foot wrap pressure sensor 40A, a conventional pressuretransducer in the preferred embodiment, converts the pressure deliveredto right foot wrap 1A from accumulator 37 into an electrical signalrepresentative of that pressure. An amplifier and an analog-to-digital(A/D) converter (not shown) on air control board 50 convert thatelectrical signal to a digital signal readable by micro-controller 41.Micro-controller 41 then processes that pressure signal and sendssolenoid control information to solenoid drive circuits (located oncontrol board 41). Those drive circuits then control right solenoidinflate valve 36A and right vent solenoid valve 32A. Control of thesolenoid inflate valve 36 and vent solenoid valve 32 by micro-controller41′ will be discussed herein with reference to the flow charts shown inFIGS. 10-12.

[0102] Pressure transducer 40C is identical to transducers 40A and 40Bbut is provided to sense the pressure in accumulator tank 37—not footwraps 1A or 1B. Specifically, the air port of sensor 40C is in directfluid communication with tank 37 through sealed line 337. The ultimatefunction of sensor 40C is to sense the drop in pressure after eachopening operation of valves 36A or 36B, thereby giving controller 41′ anindication of whether air is flowing freely out of tank 37.Micro-controller 41′ uses that pressure reading for diagnostic displayand audible alarm purposes. Micro-controller 41′ determines if thepressure is too low, based on a digital signal from the A/D converterassociated with the appropriate pressure transducer 40. Micro-controller41′, in combination with the pressure transducer 40C, thus, serves as ameans for detecting errors in the operation of system 500 in itspreferred embodiment—specifically errors due to obstruction in air flowto (and thus from, as well) the foot wraps 1A and 1B. If either line 28Aor 28B are kinked, the pressure in tank 37 will not drop after openingthe respective valve 36A or 36B. If controller 41′ determines thepressure drop sensed by sensor 40C does not exceed a threshold levelcorresponding to roughly 5mm Hg for five consecutive cycles, thecontroller 41′ concludes there is a kink in line 28A or 28B and signalsan audible alarm and visual alarm. In more detail, if the pressure dropafter valve opening is too low, microcontroller 41′ increments an errorcounter. Micro-controller 41′ determines if the error counter is greaterthan or equal to a value of five. Then, if the error counter is greaterthan or equal to five, micro-controller 41′ turns on an audible alarm,although the pump unit 501 continues to operate as before. As will beapparent to those of skill in the art, A/D converters (not shown) areassociated with each sensor 40A-40C to enable interface with controller41′.

[0103] Referring to the flow chart shown in FIGS. 10-12,micro-controller 41′ control of the preferred embodiment of the presentinvention will be described. Preferably, micro-controller 41′ is aconventional micro-controller such as Signetic's 800552 controller,which has one RAM chip 47 (along with other conventional components)integral therewith. After the power is turned on by depressing switch66, micro-controller 41′ actuates an initialization signal to itshardware components including the circuits controlling the compressor38, the solenoids 32 and 36, and display 46. In step 103,micro-controller 41 places zeros in the variables contained in randomaccess memory (RAM) 47. When the foot pump is powered down, its presentconfiguration settings, referred to as power down settings, are storedin EPROM 48 and may be used as default settings for the next power up.Accordingly, in step 104, the power down settings stored in EEPROM 48are read and stored in RAM 47.

[0104] Sequential polling of PULSE ON/OFF switch 43, operator selectionswitches 44A, 44B, and 44C, and OPTIONS switch 45 occurs every 25milliseconds, as shown in steps 105-111. Step 106 informsmicro-controller 41′ to start its polling with switch 1. In step 107,micro-controller 41′ stores the state of the polled switch in RAM 47 andin step 108 compares that state with its previous state. If the switchhas changed states, micro-controller 41′ advances to step 109 andexecutes the selected switch function and stores the operator setting ordefault setting retrieved from ROM 52 (actually a conventional EEPROM inthe preferred embodiment) into RAM 47. Micro-controller 41′ thenadvances to step 110. Alternatively, micro-controller 41′ advancesdirectly to step 110 if the switch did not change state. In step 110,micro-controller 41′ determines if the last switch has been polled. Ifthe last switch has not been polled. micro-controller 41′ increments tothe next switch in step 111 and returns to step 107 where it reads thestate of that switch. Once all the switches have been polled,micro-controller 41′ advances to step 112.

[0105] In step 112, micro-controller 41′ reads the settings from astatus register located in RAM 47 to determine which foot (if either)will be processed for the current cycle. If Pulse is switched OFF,micro-controller 41′ advances to step 127 and updates the operating timemeter, which records total operating time. In step 128, micro-controller41′ actuates signals to both power distribution board 49 and pressurecontrol board 50 to control unit 501. More specifically, in response tothe signals of step 128, power distribution board 49 turns compressor 38on or off, and pressure control board 50 energizes or de-energizes (asnecessary) the inflate solenoid valves 36A and 36B and/or the ventsolenoid valves 32A and 32B. In step 129, micro-controller 41′ refreshesthe present display of LCD assembly 46 as necessary. After updating thedisplay on LCD assembly 46, micro-controller 41′ returns to step 105 tocontinue the present foot function mode. This loop is repeated every 25milliseconds.

[0106] The four foot function modes will now be discussed. This path isfollowed anytime that PULSE is switched ON. Micro-controller 41′sequentially and repeatedly advances through the following foot functionmodes: deflate to pre-inflate, pre-inflate to inflate, inflate to hold,and hold back to deflate. The vent valve and the inflate valve in thepreferred embodiment are identical body-ported three-way solenoidvalves. The vent solenoid valve is fluidly connected to be normallyopened, and the inflate solenoid valve is connected to be normallyclosed. In the deflate mode, the vent solenoid valve corresponding tothe inflated foot wrap opens releasing any air pressure in theinflatable bladder. The pre-inflate mode causes the normally opened ventsolenoid valve to close, while the inflate solenoid valve remainsclosed. Then during the inflate mode, the inflate solenoid valvecorresponding to the foot wrap that is to be inflated is opened,allowing air pressure to fill the inflatable bladder while the ventsolenoid is held closed. After each inflate mode, the opened inflatesolenoid valve closes while the vent valve remains closed, thusmaintaining the air pressure in the foot wrap during the hold mode.

[0107] The above cycle continuously repeats during foot pump operation.However, when the pump unit 501 is initially turned on, the beginninginflate modes operate under a ramping function. The ramping feature isbeneficial because the pressure sensation delivered to a patient's footduring the first few inflate modes may startle the patient. Accordingly,the ramping feature reduces patient alarm by allowing the patient togradually become acclimated to the pressure pulses delivered to thepatient's foot. Upon system start-up, the initial pressure in the firstinflate mode is low because the inflate solenoid valve is only brieflyenergized (25 milliseconds in the preferred embodiment). During eachsubsequent inflate mode, the inflate solenoid valve energization timeincreases by 25 milliseconds until that energization time reaches theoperator selected or default pressure level, and the foot pump isdelivering the desired pressure to the patient's foot, Other embodimentsinclude ramping feature inflate times starting at 100 milliseconds andincreasing by 50 millisecond increments.

[0108] Again referring to step 112, if the left or right foot isselected, micro-controller 41′ advances to step 113 and reads the valueof the foot function counter. The value stored in the foot functioncounter represents the time remaining for the foot function in progress.Foot functions include inflate, hold, deflate and pre-inflate. Each footfunction counter value is determined on the basis that micro-controller41′ requires 25 milliseconds (in the preferred embodiment) to executesteps 105-129, thereby completing one processing loop, which includes afoot function counter decrement (step 115). For example, if the userselects a one second hold time, micro-controller 41′ places a value of40 in the foot function counter. Micro-controller 41′ enters that valueinto the foot function counter at the beginning of a hold functionbecause 40 loops through steps 105-129 equals one second (40 loops times25 milliseconds equals 1000 milliseconds, or one second). Therefore, asmicro-controller 41′ decrements the hold mode foot function counterduring each pass through step 115, the inflate solenoid valves and ventsolenoid valves will remain closed for one second.

[0109] The hold, deflate, and pre-inflate modes have fixed foot functioncounter values corresponding to each operator or default time selectionas calculated above. However, because of the pressure ramping feature,the inflate mode foot function counter begins at 1 (corresponding to areal time of 25 milliseconds) and is incremented by 1 during eachsubsequent inflate mode until the desired pressure is reached. Thus, thesolenoid valves remain open an additional 25 milliseconds through eachsubsequent inflate cycle. Once the desired pressure is achieved.micro-controller 41′ no longer increments the inflate mode foot functioncounter.

[0110] Although for the purposes of a preferred embodiment,micro-controller 41′ requires 25 milliseconds to perform the functionsdisclosed in steps 105-129, one of ordinary skill in the art willreadily recognize that any delay time could be properly substituted.Variations on the ramping feature could also be substituted. As anexample that other embodiments are being adapted to include solenoidenergizing time at 100milliseconds is initiating inflation andincrementing it by steps of 50 milliseconds (as opposed to the 25/25times described previously).

[0111] In step 113, if the foot function counter is not zero,micro-controller 41′ advances to step 115 and decrements the footfunction counter by 1. Micro-controller 41′ then advances to step 118.If the foot function counter is zero, micro-controller 41′ has completeda foot function inflate, hold, deflate or pre-inflate. Accordingly,micro-controller 41′ advances to step 114 and increments to the nextfoot function and places the value corresponding to that foot functioninto the foot function counter. Next, in step 116, micro-controller 41′determines whether the present foot function is in the inflate mode. Ifthe foot function is in the inflate mode, micro-controller 41′ advancesto step 117 and increases the previous foot function inflate count by 1(corresponding to 25 milliseconds) for use during the next inflatecycle. However, if the inflate mode has reached the user selected ordefault pressure as determined in step 120 (discussed herein),micro-controller 41′ will not increment the foot function counter. Ifthe foot function is not in the inflate mode, micro-controller 41′advances directly to step 118.

[0112] In step 118, micro-controller 41′ determines whether the footfunction is in the deflate, pre-inflate, hold, or inflate mode. If instep 118, the foot function was in the inflate mode, microcontrollerreads a pressure signal from the respecting pressure sensor and advancesto step 120. In step 120, micro-controller 41′ determines if thepressure in the foot wrap is too high. That is, micro-controller 41′determines if the foot wrap pressure has exceeded the operator selectedor default pressure. If the measured pressure is below the operatorselected or default pressure, micro-controller 41′ advances to step 127and updates the operating time meter. In step 128, if the solenoid valvecorresponding to the foot wrap to be inflated is de-energized,micro-controller 41′ energizes it via pressure control board 50.However, if the solenoid valve 36 is already energized, microcontroller41′ rewrites the energization signal to pressure control board 50. (Notethat the vent solenoid status is updated as well.) Micro-controller 41′then updates LCD assembly 46 and returns to step 105 to continue thepresent foot function.

[0113] However, if, in step 120, micro-controller 41′ determines thatthe actual pressure is above the desired pressure, it advances to step122. In step 122, micro-controller 41′ increments to the next footfunction (hold in this case) and places the foot function counter valuecorresponding to that foot function in the foot function counter.Micro-controller 41′ then updates the operating time meter in step 127.In step 128, micro-controller de-energizes, via pressure control board50, the inflate solenoid valve that had been energized during theinflate mode. The vent solenoid status is updated as well. Next,micro-controller 41′ updates LCD assembly 46 and returns to step 105 forexecution of the next foot function mode.

[0114] Micro-controller 41′ is provided with two methods in the inflatemode to stop compressed air delivery to the foot wraps. First,micro-controller 41′ monitors the pressure developed in the foot wrapduring inflation, and if that pressure exceeds the operator selected ordefault pressure value, micro-controller 41′ immediately increments tothe next foot function and closes the energized solenoid valve (steps120, 122 and 128). Alternatively, if the air pressure ever exceeds thedesired pressure, micro-controller 41′ delivers compressed air for theincrementing interval defined in the foot function counter. That is,micro-controller 41′ allows inflation of the foot wrap until the inflatemode foot function counter is decremented to zero. Once the footfunction counter reaches zero, micro-controller 41′ increments to thenext foot function and de-energizes the energized solenoid valve,thereby stopping air pressure delivery to the foot wrap. Thus,micro-controller 41′ stops compressed air delivery to the foot wrap wheneither the inflation pressure exceeds the user specified or defaultvalue, or the inflate mode foot function counter reaches zero, whicheveroccurs first. (As noted earlier in this document, the inflate time valvein the preferred embodiment is ramped up in 25 millisecond intervals.)

[0115] Again referring to step 118, if the foot function is in the holdmode, micro-controller 41′ advances to step 119 and determines whetherat least ¾ of a second of the hold time has elapsed. If at least ¾ of asecond of the hold time has not elapsed, micro-controller 41′ advancesto step 127 and updates the operating time meter. In step 128, if theinflate mode foot function counter was completely decremented to zero,micro-controller 41′ will de-energize via pressure control 50 thesolenoid valve energized during the preceding inflate mode. However, ifthe inflate mode was ended because the air pressure in the foot wrapbecame too high, the energized solenoid will already have beende-energized, and micro-controller 41′ will only rewrite thede-energization signal. Micro controller 41′ then updates the display onLCD assembly 46 in step 129 and advances to step 105 to continue thepresent foot function mode.

[0116] If the elapsed hold time is equal to ¾ of a second,micro-controller 41′ reads the pressure value measured by the respectivepressure sensor and advances to step 121. Step 119 provides a ¾ of asecond delay before pressure measurement to permit the air pressure inthe foot wrap to settle so that the pressure sensor makes an accuratepressure reading. Micro-controller 41′ uses that pressure reading fardiagnostic display and audible alarm purposes. In step 121,micro-controller 41′ determines if the pressure is too low, based on adigital signal from the A/D converter associated with the appropriatepressure transducer 40. Micro-controller 41′, in combination with thepressure transducer 40, thus, serves as a means for detecting errors inthe operation of system 500 in its preferred embodiment. If the pressureis too low micro-controller 41′ advances to step 123 and increments anerror counter. In step 124, micro-controller 41′ determines if the errorcounter is greater than or equal to a value of 5. If the error counteris greater than or equals to 5, micro-controller 41′ turns on an audiblealarm in step 125 and advances to step 127. Although the audible alarmsounds, the pump unit 501 continues to operate, and no changes are made.In step 127, micro-controller 41′ updates the operating time meter. Instep 128, micro-controller 41′ rewrites the present actuation signals topower distribution board 49 and pressure control board 50. In step 129,micro-controller 41′ updates the display as necessary on LCD assembly 46and returns to step 105 to continue the present foot function mode.However, if the error counter is below 5, micro-controller 41′ advancesdirectly to step 127 without turning on the audible alarm. In steps127-129, micro-controller 41′ updates the operating time meter, rewritesthe actuation signals to power distribution board 49 and pressurecontrol board 50, and updates the display as necessary on LCD assembly46. Micro-controller 41′ then advances to step 105 to continue thepresent foot function.

[0117] Again referring to step 121, if the measured pressure is not toolow, micro-controller 41′ advances to step 126, turns off the audiblealarm (if it was on), and sets the error counter to zero.Micro-controller 41′ then advances to steps 127. In steps 127-129,micro-controller 41′ updates the operating time meter, rewrites theactuation signals to power distribution board 49 and pressure controlboard 50, and updates the display as necessary on LCD assembly 46.Micro-controller 41′ then advances to step 105 to continue the presentfoot function.

[0118] Referring again to step 118, if the foot function is in thedeflate or pre-inflate mode, micro-controller 41′ advances directly tostep 127 to update the operating time meter. In step 128,micro-controller 41′ changes the actuation signal to pressure controlboard 50 to either energize or de-energize the vent and inflate solenoidvalves dependent upon whether the foot function mode is deflate orpre-inflate. For example, if the foot function is in the deflate mode,the vent solenoid valve will open and the inflate solenoid valve will beclosed to allow the deflation of the inflated foot wrap. However, if thefoot function is in the pre-inflate mode, the vent solenoid valve willbe closed in preparation for the next inflate foot function mode. Alsoin step 128, micro-controller 41′, via power distribution board 49,stops, starts or continues the delivery of power to compressor 38. Aftermicro-controller 41′ updates LCD assembly 46 in step 129, it advances tostep 105 where the loop is repeated every 25 milliseconds.

[0119] Operation of the power down memory of the preferred embodiment ofthe present invention will be described in reference to the flowchartshown in FIG. 4. In step 130, if the power is turned off or there is apower line transient (e.g. a power surge or noise), micro-controller 41′executes the power off interrupt. In step 131, micro-controller 41′executes a software filter loop to reduce susceptibility to power linenoise transients. In step 132, micro-controller 41′ determines if thepower has been turned off or if the power line merely experienced atransient. If the power line experienced a transient, the interruptroutine is exited and the pump unit 501 continues to operate normally.If micro-controller 41′ determines that AC power has been turned off,micro-controller 41′ advances to step 133 and determines if the powerhas been on for more then 3seconds. If the power has been on for morethan 3 seconds, micro-controller 41′ advances to step 134 and writesdate into EEPROM power down memory 48 values representing the lastoperator entered foot function settings. Micro-controller 41′ thenadvances to step 135 and exits the power down routine. However, if, thepower has not been on more than 3 seconds, micro-controller 41′ advancesto step 135 and exits the power down routine.

[0120] FIGS. 13-18 show the general shape of the pump housing 20 whichhas also been described with reference to FIG. 1. Note though that thedetails of console 42 and connectors 22A and 22B have been omitted inFIG. 14 to focus attention on the shape of housing 20. Screws 201-204(shown in FIG. 15) are common screws which secure front plate 26 to rearplate 27. Of course, other conventional connectors could be usedinstead. Spacers 205-208 on the underside of housing 20 allow for levelplacement of the pump unit 501 on a flat surface. Spacers 210 and 211,along with spacers 205 and 206, ensure free flow of air into the pumpunit's air intake 215, even when the unit is mounted snugly against afoot board 600 (FIG. 18) of a hospital bed.

[0121] Assembly of the back plate 26 is best understood with referenceto FIG. 19. As shown therein, air intake filter assembly 220 is mountedto the inside surface of back plate 26. Assembly 220 basically includesa primary filter 221 and a secondary filter 222 together with mountingbracket 223. Primary filter 221 is fairly porous to allow free intake ofair while secondary filter 222 is positioned to surround theinternally-exposed edges of primary filter 221 to ensure that all intakeair is adequately filtered even if it circumvents primary filter 221.Bracket 223 is rigidly secured to the back plate 26 in a manner thatcages primary filter 221 in place over intake 215. Secondary filter 222is glued in place afterwards. The location of intake 215 is ideal as itis partially shielded from liquids and foreign objects when housing 20is operatively mounted on a foot board 600 of a hospital bed. Suchliquids and foreign objects, naturally, might otherwise impede theoperation of unit 501, much less the free flow of air into inlet 215.Spacers 210 and 211 preferably provide a ⅜ inch separation between thefoot board 600 (shown in phantom line in FIG. 18) and intake 215 toensure free air flow therein.

[0122] Retractable mounting hooks 21A and 21B are shaped as shown bestin FIGS. 17-19. Hooks 21A and 21B are similar to each other and aresymmetrically mounted in a pivotal manner to plate 26. The pivotalmounting is best shown in FIG. 19, with reference to hook 21A. As showntherein, hook 21A is pivotally mounted by means of an integral shank 230that fits snugly through a hole 231 in an irregular socket 240 (numberedin FIG. 18) formed in plate 26. Hole 231 is substantially coaxial withhole 232 so that the hooks 21A & B pivot in parallel planes that areperpendicular to back plate 26 in the preferred embodiment. Onceinserted through hole 231, shank 230 is pivotally secured therein by alocking push ring 234. A spring washer 235 is positioned on the shank230 to spring bias the shank through the hole in the same manner as aBellview washer. Although not clear in FIG. 19, portions of springwasher 235 are bent in a manner that provides such a spring action. Thelocking push ring 234 is appropriately sized and flared around its innercircumference in a conventional manner so that it can be pushed ontoshank 231 but the flare prevents it from sliding back off the shank 231.Thus ring 234 provides a permanent pivotal connection for hook 21A.

[0123] Although not shown very well in the drawings, it is preferredthat slight tongue and groove reliefs are provided on the matingsurfaces between the hook 21A and plate 26 so that hook 21A tends toclick into place in either its fully retracted or fully extendedpositions. The spring bias of washer 235 helps provide such a clickingaction as it tends to retain hook 21A in its clicked position. FIG. 17shows hook 21A in its fully retracted position, and FIG. 18 shows hook21B in its fully extended position. Socket 240 is shaped to neatlyreceive hook 21A when it travels from its fully extended to its fullyretracted positions.

[0124] The innovative shape of hook 21A is best appreciated withreference to FIG. 18. Progressing from shank 230 outward, portions ofhook 21A are referred to as shoulder 245, elbow 247, forearm 243, andknob 241, all formed as an integral member which is generallyprogressively thinner toward knob 241. The inner face 252 of hook 21Aapproximates a planar surface (except for the protrusion of shank 230)so that hook 21A pivots freely into socket 240. Knob 241, on the otherhand, protrudes outward in a direction opposite shank 230 to roughlytwice the thickness of forearm 243. Knob 241 is cylindrical in shapewith its leading outer corner truncated and rounded to form a smoothfinger pad 251. Finger pad 251 enables manual pivoting of hook 21A fromits fully retracted to its fully extended position. The point ofjuncture between knob 241 and forearm 243 is referred to as wrist 242.

[0125] The forwardmost edges 244 and 246 of forearm 243 and shoulder 245are substantially planar sections which are parallel to axis 250 ofshank 230 and, therefore, appear linear in FIGS. 17 and 18. Althoughfillets are provided at wrist 242 to reduce stress concentrations, theplane of edge 244 is roughly perpendicular to the cylindrical surface ofknob 241. Knob 241 thus forms a protruding lip at the distal end offorearm 243, and this lip helps retain pump unit 501 on foot board 600even if it is knocked outward from the foot board.

[0126] Because standard foot boards range from ½ to {fraction (1 1/2)}inches in width, it may also be helpful to consider some of thedimensions of hook 21A. The pivot axis 250 for the hook 21A ispreferably as high as possible on housing 20 and should be at least highenough to ensure the center of gravity of pump unit 501 is lower thanthe center of distal knob 241, to help ensure against tipping. Toaccommodate a range of foot board sizes, the distance between the crease248 of elbow 247 and the planar surface 26′ of back plate 26 (when hook21A is fully extended) is ⅞ inches, thereby snugly receiving thesmallest of standard foot boards while leaving the ⅜ inch space providedby spacers 210 & 211. At the opposite extreme, the forwardmost edge ofknob 241 is {fraction (1 7/8)} inches from surface 26′ (when fullyextended), thereby snugly accommodating the widest of standard hospitalfoot boards. Moreover, for any foot boards in the range of standardsizes, the weight of pump unit 501 tends to pull surface 26′ downwardand thus closer to foot board 600 due to the constant slope of edge 244,until each of spacers 210 & 211 engage the foot board 600. Referring toangle alpha (FIG. 18) the slope of edge 244 is such that alpha is anobtuse angle less than 135 degrees. Preferably, alpha is roughly 115degrees. With such construction, housing 20 is adapted for snug, secureand neat mounting on hospital bed foot boards 600 in the full range ofstandard sizes.

[0127] Although the present invention has been described in terms of theforegoing preferred embodiments, such embodiments are merely exemplaryof the present invention. As will be apparent to those of ordinary skillin the art, many other alternatives, equivalents, modifications,objects, substitutions, variations and the like, of varying degrees,will fall within the scope of the present invention. For instance, thenumber, specifications and locations of various components or thesequence, number, and complexity of various steps can generally bemodified to some degree while still serving substantially the samepurposes of the present invention. As a particular example, air controlboard 50 and control board 41 may be combined into a single integratedcircuit board to minimize costs and space constraints, as Applicant hasdone in alternative embodiments. Accordingly, nothing in the foregoingdetailed descriptions limits the scope of the present invention in anyrespect, but rather that scope is defined instead only by the claimswhich follow, construed as broadly as possible.

I claim:
 1. A medical apparatus for affecting blood circulationcomprising: a foot wrap having an inflatable bladder for applyingpressure to a patient's foot; a pressure source for supplying pressureto said foot wrap; a line in fluid communication with said pressuresource; said line having an expansion reservoir therein for simulatingthe pressure in the bladder caused by the pressures losses in theapparatus; a pressure sensing means including a pressure sensorconnected to said line, downstream of said expansion reservoir, forsensing the amount to pressure supplied by said pressure source andconverting the sensed amount into a signal; and a control means incommunication with said pressure sensing means to adjust the amount ofpressure supplied by said pressure source.
 2. The apparatus of claim 1wherein said line further comprises at least one restrictor to restrictthe flow of air pressure to said pressure sensor.
 3. The apparatus ofclaim 1 wherein said signal includes an analog voltage signal, and saidpressure sensing means further comprises an analog to digital conversionmeans to convert said voltage signal into a digital signal.
 4. Themedical apparatus of claim 1 wherein said control means comprises: amicrocontroller; and a plurality of solenoid valves controlled by saidmicro-controller to adjust the amount of pressure supplied by saidpressure source to said foot wrap.
 5. The apparatus of claim 4 whereinsaid micro-controller is operable to read said digital signal from saidpressure sensing means and to open and close said solenoid valves inresponse to the read signal.
 6. The apparatus of claim 4 wherein saidcontrol means further comprises an error detection means for determiningwhen pressure supplied by said pressure source is either to high or tolow.
 7. The apparatus of claim 4 wherein said control means furthercomprises: an operator console having programmable keys to enter usersettings; and memory means for storing said user settings to beprocessed by said micro-controller.
 8. The apparatus of claim 7 whereinsaid operator console further comprises a liquid crystal display.
 9. Theapparatus of claim 7 wherein said memory means comprises anelectronically erasable programmable read only memory.
 10. A medicalapparatus for cyclically applying pressure to a foot, comprising: aflexible fabric foot wrap formed from two sheets and having aninflatable bladder therein, a connector opening into the inflatablebladder and suitable for connection to a source of pressurized fluid;said foot wrap having a first tab formed from at least one of said twosheets for releasably securing the device to a human foot about thearch, the first tab having a releasable connector at its distal end;said foot wrap having a second tab formed from at least one of said twosheets for releasably securing the device to a human foot about theheel, the second tab being generally perpendicular to the first tab, thesecond tab having a releasable connector at its distal end; said footwrap having an exterior surface portion on one of said sheets compatiblewith said releasable connectors so that a connection may be formed whensaid connectors are pressed against said surface; a source for supplyingpressurized fluid to said inflatable bladder; pressure sensing means formeasuring the amount of pressure supplied by said source; and a controlmeans in communication with said pressure sensing means to adjust theamount of pressure supplied by said source.
 11. The medical apparatus ofclaim 10, further comprising: a housing for releasably mounting saidsource on the foot board of a standard hospital bed, said housingcomprising a pair of opposite, retractable mounting hooks having slopedsurfaces for biasing the source toward said foot board and having knobsat the distal ends thereof for helping retain the hooks on the footboard; and said hooks further having a horizontal bearing surface forengaging the top of foot boards having smaller widths.
 12. An inflatabledevice for pneumatic compression of the foot, comprising: an inflatablechamber for wrapping around the foot and compressing the foot wheninflated; a strap formed integral with said first member for wrappingaround the lower portion of a leg and securing the first member inplace; and said strap comprising means for cushioning a skin-engagingsurface of said strap for minimizing localized pressure concentrationsrelated to said surface.
 13. A medical apparatus for affecting bloodcirculation comprising: a foot wrap having an inflatable bladder forapplying pressure to a patient's foot; a pressure source for supplyingpressurized gas to said foot wrap; a line in fluid communication withsaid pressure source; a control means having a valve means forcontrolling the supply to supply of said pressurized gas; a pressuresensing means including a pressure sensor connected to said line forsensing the amount of pressurized gas being supplied by said pressuresource upon opening of the valve means and converting the sensed amountinto a signal for controlling the valve means; and said control meansbeing operatively connected with said pressure sensing means turn offthe valve means to adjust the amount of pressurized gas being suppliedby said pressure source.
 14. A method for affecting blood circulationcomprising: applying a foot wrap having an inflatable bladder forapplying pressure to a patient's foot; supplying pressurized gas from apressure source to said foot wrap; sensing the amount of pressurized gasbeing supplied by said pressure source in an expansion reservoir forsimulating the pressure in the bladder caused by pressures losses andconverting the sensed amount into a signal for controlling the amount ofpressurized gas being supplied by said pressure source.
 15. A method foraffecting blood circulation comprising: applying a foot wrap having aninflatable bladder for applying pressure to a patient's foot; supplyingpressurized gas from a pressure source to said foot wrap; controllingthe supply of pressurized gas with a valve means; sensing the amount ofpressurized gas being supplied by said pressure source upon opening ofthe valve means and converting the sensed amount into a signal forcontrolling the valve means; and turning off the valve means to adjustthe amount of pressurized gas being supplied by said pressure source.